Digital Radiology (DR) is a technology that uses flat panel detectors to produce digital X-ray images directly. DR detectors are substantially based on standard area (which developed historically from the production line sizes of x-ray film and x-ray film cassettes) devices having a medium that transfers high energy X-ray photons into electrical charge which are distributed and segmented into a matrix of pixels forming an image. For example, the charge at each pixel location may be digitized and the whole matrix of pixels forms an X-ray image of the converted charge. The X-ray image may then be transmitted and displayed on a computer screen.
There are two main major technologies generally used in such flat panel detectors: 1) direct digital detectors, where the X-ray photons are converted directly into charge by a flat surface layer of specific materials such as amorphous Silicon or amorphous Selenium; and 2) indirect digital detectors where an energy converter layer is used to convert the high energy X-ray photons into a very high number of lower energy light photons (e.g., photons in the visible spectrum). These lower energy light photons may then be converted into electrical charge by a large matrix semiconductor device. As discussed above, the charge at each pixel location may be converted into a digital value representing an intensity of the pixel in the digital X-ray image. However, such DR flat panel detectors are expensive and relatively complicated to manufacture.
To reduce cost and complexity, the relatively expensive large area semiconductor layers may be replaced with one or more semiconductor cameras. The cameras may be relatively inexpensive small area silicon pixel matrix cameras, such as those formed from arrays of charge-coupled devices (CCDs). Thus, the lower energy light photons coming out of the energy transfer layer (e.g., a phosphor screen) pass through a large lens and the image is focused on the small silicon chip to produce the transfer to charge and then into a digital image.